The present invention relates, in general, to electronics, and more particularly, to semiconductors, structures thereof, and methods of forming semiconductor devices.
In the past, the semiconductor industry utilized various methods and structures to build semiconductor devices to control an ignition coil of an internal combustion engine, such as an engine for a vehicle such as a car, etc. In some embodiments, a semiconductor load switch or load switch was connected to a primary side of an ignition coil to control a spark plug of the engine. In some embodiment, the load switch could be an insulated gate bipolar transistor (IGBT). A controller of the semiconductor device enabled and disabled the load switch to create a large voltage on a secondary side of the ignition coil resulting in a spark through the spark plug. In another event that other elements that are connected to ground failed, the increased current through the failed elements could cause an open circuit in the fuse in order to protect the system.
In some instances, there could be a failure of the load switch or elements of the semiconductor device that could result in a large current through the coil which could eventually damage the semiconductor device or possibly the coil, or the engine, or the vehicle. In some conditions, the large current may also flow through the element that failed, which could also lead to damage of the coil or of the engine, among other things. Some embodiments included a fuse that was connected between a voltage source, and the primary side of the ignition coil and/or elements connected to ground. In the event that the load switch failed, the increased current through the ignition coil could cause an open circuit in the fuse in order to protect the system.
In some applications, the sensitivity of the fuse may be too high and the fuse may form an open circuit during normal operating conditions. Thus, the semiconductor device and, in some case, together with the vehicle component which include the semiconductor device may have to be replaced in order to restore operational condition to the system. Replacing the semiconductor device resulted in increased cost. Additionally, the reliability of the vehicle may be degraded. In other conditions, the sensitivity of the fuse may be too low and the semiconductor device may be damaged before the fuse forms the open circuit. In this example, the semiconductor device would also have to be replaced which would lead to increased cost. In some cases, the failure could result in more serious damage and may even result in a fire.
Accordingly, may be desirable to have a device or method that can more accurately protect the semiconductor device from damage, and/or more accurately protect the semiconductor device from a short circuit condition, and/or that can reduce operating costs of the ignition system.
For simplicity and clarity of the illustration(s), elements in the figures are not necessarily to scale, some of the elements may be exaggerated for illustrative purposes, and the same reference numbers in different figures denote the same elements, unless stated otherwise. Additionally, descriptions and details of well-known steps and elements may be omitted for simplicity of the description. As used herein current carrying element or current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control element or control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Additionally, one current carrying element may carry current in one direction through a device, such as carry current entering the device, and a second current carrying element may carry current in an opposite direction through the device, such as carry current leaving the device. Although the devices may be explained herein as certain N-channel or P-channel devices, or certain N-type or P-type doped regions, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. One of ordinary skill in the art understands that the conductivity type refers to the mechanism through which conduction occurs such as through conduction of holes or electrons, therefore, that conductivity type does not refer to the doping concentration but the doping type, such as P-type or N-type. It will be appreciated by those skilled in the art that the words during, while, and when as used herein relating to circuit operation are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay(s), such as various propagation delays, between the reaction that is initiated by the initial action. Additionally, the term while means that a certain action occurs at least within some portion of a duration of the initiating action. The use of the word approximately or substantially means that a value of an element has a parameter that is expected to be close to a stated value or position. However, as is well known in the art there are always minor variances that prevent the values or positions from being exactly as stated. It is well established in the art that variances of up to at least ten percent (10%) (and up to twenty percent (20%) for semiconductor doping concentrations) are reasonable variances from the ideal goal of exactly as described. When used in reference to a state of a signal, the term “asserted” means an active state of the signal and the term “negated” means an inactive state of the signal. The actual voltage value or logic state (such as a “1” or a “0”) of the signal depends on whether positive or negative logic is used. Thus, asserted can be either a high voltage or a high logic or a low voltage or low logic depending on whether positive or negative logic is used and negated may be either a low voltage or low state or a high voltage or high logic depending on whether positive or negative logic is used. Herein, a positive logic convention is used, but those skilled in the art understand that a negative logic convention could also be used. The terms first, second, third and the like in the claims or/and in the Detailed Description of the Drawings, as used in a portion of a name of an element are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments described herein are capable of operation in other sequences than described or illustrated herein. Reference to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but in some cases it may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art, in one or more embodiments.